System of control.



N. W. STORER.

SYSTEM OF CONTROL.

APPLICATION FILED SEPT. 8. 1914. RENEWED JULY 6,1917.

Patented Nov. 6, 1917.

3 SHEETSSHEET I.

llllllll nuxXuw INVENTOR fi o/man f/bl al WITNESSES:

AZTTORNEY N. W. STOBER.

SYSTEM OF CONTROL.

APPLICATION FILED SEPT. s. 1914. RENEWED JULY 5. 1911'.

Patented Nov. 0, 1917.

3 SHEETS-SHEET 2- aa E U mQ Mk u NE k kk Rs Q 8mm Q v3 mIR G} WITNESSES INVENTOR War/m0 14/ (13 0/10 ATTORNEY N. W SIURER.

SYSTEM OF CONTROL.

APPLICATION FILED SEPI. 8. I914- RENEWED JULY a. nu 7.

Patented Nov. 6, I917.

3 SHEETS-SHEET 3- f 1:9. 1

* INVENTOR Norma/7 WJfwer a; WITNESSES ATTORNFY UNITED STATES PATENT OFFICE.

NORMAN W. STORER, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SYSTEM OF CONTROL.

Specification of Letters Patent.

Patented Nov. 6, 191 '7.

Application filed September 8, 1914, Serial No. 860,608. Renewed July 6, 1917. Serial No. 179,079.

To all whom it may concern:

Be it known that I, NORMAN W. STORER, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Control, of which the followingis a specification.

My invention relates to systems of electric motor control and it has special reference to such systems as are adapted for use in electric railway service.

One object of my invention is to-provide a regenerative control system which shall return to the supply circuit a greater percentage of the kinetic energy of the momentum-driven or gravity-driven vehicle with which the motors are associated than has been the case heretofore.

In a more limited aspect, the object of my invention is to provide, in combination with a series-parallel control system for accelerating the motors, a parallel-series control system for electrically retarding the motors and the vehicle.

Another object of my invention is to provide a control system which may be readily adapted for regeneration with the motor ar-, matures initially either in parallel or in series relation, according as the vehicle is traveling at a relatively high or at a relatively low speed. i

Another object of my invention is to automatically maintain a substantially constant regenerated current in each motor throughout the parallel-series operation of I the generating machines.

A further object of my invention is to provide a control system of the above-indicated character which shall embody all the desirable operating features to be found in prior systems of this general class and Which shall, at the same time, employ a materially reduced number of pieces of control apparatus for satisfactorily accomplishing the intended purpose. In fact, in some instances, the number of control members required has been reduced one-half, thereby making for a relatively inexpensive and economical control system.

Another'object of my invention is to provide completely automatic meansfor con necting the momentum-driven motor armatures in parallel relation when a predetermined voltage relation exists between the voltage generated at the armature terminals and the line voltage, for gradually increasmg the motor field strengths to maintain a substantially constant armature current as the motor speed decreases, for accomplishmg the transition from parallel to series relation of the motor armatures Without entlrely opening the circuit, and for then maintaining a substantially constant regenerated current to a relatively low speed of the vehicle, when the mechanical brakes may be efhciently applied to bring the vehicle to a complete stop.

Another object of my invention is to provlde means, in the form of an air-operated interlock, for opening the regenerative circuits immediately upon the actuation of the mechanical brakes.

While my invention is particularly adapted for the control of railway vehicles, it is not limited to any class of service and may be utilized in the control ofautomobiles and other road vehicles or in the control of tial relay switch, for automatically connecting a vehicle motor to the supply circuit when the electromotive force generated at its terminals bears a predetermined relation to the voltage of the line.

I provide also a change-over switch, which may be manually or otherwise operated, to arrange the regenerative circuit connections for either parallel-series or straight series operation of the motor armatures, in accordance with the speed of the vehicle, as hereinafter described.

I provide also automatic means for arranging the parallel-connected momentumdriven motor armatures in series relation with all the field magnet windings and, subsequently, when the speed of the vehicle has decreased to a predetermined value, connecting the motors in series relation without entirely opening the circuit and while maintaining a substantially constant regenerated current. In addition to the foregoing, I so interlock the various control switches and apparatus of the system as to permitof the normal series-parallel operation of the motors in accelerating the vehicle, by adjusting the master controller in one direction, and of automatic adjustment of the circuits for regenerative braking accompanied by connection of the motors to the circuit at the proper time, by throwing the master controller in the opposite direction, or by using a second master controller.

In addition, I preferably provide, in combination with the regenerative braking system, an ordinary air'brake apparatus, which is automatically made effective when the speed of the vehicle has fallen below a relatively low value. I also provide an air-operated interlocking contact member which is connected in the control circuit of the line switches, whereby the switches are opened to stop regenerative braking when the mechanical brakes are actuated. By the utilization of the above-mentioned combination, a relatively large proportion of the kinetic energy ordinarily lost in heat is returned to the line, while, at the same time, the regenerative braking system is not relied upon when the speed of the vehicle is below a predetermined value. Consequently, the stop is accomplished in a minimum length of time, and each of the two methods of braking is employed when it is most effective. The brake shoes are materially relieved from wear and will, of course, require relatively infrequent renewal.

In my co-pending application, Serial No.

724,068. filed October 5, 1912, and assigned to the Westinghouse Electric & Mfg. Company, I have shown a control system that embraces the general principles that are emaccomplish the results formerly attained by the combined operation of the individual sets of control apparatus referred to above.

It will be observed that, by means of the above-mentioned parallel-series arrangement of the regenerating motors, whereby the motor armatures are connected in parallel relation and the field current is regulated to a predetermined limit and then the motors are disposed in series relation with field regulation again to a suitable limit, the maximum possible amount of the kinetic energy of the moving vehicle is returned to the line, thus materially increasing the efiiciency of operation.

Figure 1 of the accompanying drawings is a diagrammatic view of a system of motor control embodying my invention, the main circuit connections and the switches and control apparatus which are directly associated therewith being shown complete according to the usual diagrammatic methods of representation. The control circuits are, however, merely indicated by appropriately designated lines, in order to avoid confusion.

Fig. 2 is a diagrammatic view of the control circuits including the actuating coils and the interlocks which form parts of the main circuit switches and control apparatus shown in Fig. 1. In order to simplify the circuit connections, however, the interlocks which, as shown in Fig. 1, are grouped with the various switches, are distributed and each of them is marked to indicate the switch or control device with which it is associated and by which is it operated.

Figs. 3, 4, 5 and 6 are simplified diagram matic views showing various circuit connections during the regenerative braking period of the motors.

Referring to Fig. 1 of the drawings, the system here shown comprises a supply circuit conductor which, for convenience, is marked Trolley; a return circuit conductor which is marked Rail; a pair of electric motors having armatures marked respectively M#1 and M#2 and field magnet windings marked respectively F1 and F2; two pair of line switches marked LS1, M1, LS2 and M2; a two-part resistor section one part of which is adapted to be short-oilcuited by a switch SP throughout regeneration and the whole of which may be shortcircuited by a switch S2; a plurality of resistor sections one of which may be shortcircuited by a switch R1, two of which may be short-circuited by a switch R2, and all three of which may be short-circuited by a switch R3; a second group of resistor sections, one of which may be short-circuited by a switch RRl, two of which may be shortcircuited by a switch RR2. andall three of which may be short-circuited by a switch RR3; a third group of resistor sections that are used only during regeneration, oneof which may be short-circuited by a switch P1, two of which may be short-circuited by a switch P2, and all three of which may be short-circuited by a switch P3: other resistor sections which may be respectively short-cir- COS that is associated with the several mo tor armatures,-and which is normally adapted to occupy a position designated by acceleration and parallel-series regeneration,

' and which may be thrown to a second position marked Series Regeneration.

' In order to avoid confusion, each resistnr section will hereinafter be designated by the reference character which is applied to its short-circuiting or excluding switch; for example, the resistor short-circuited by the switch S1 will be termed the S1 resistor. Similarly, one of the motors will be referred to as motor M#1, which is the reference character applied to its armature, and the other as motor M#2.

The operation of the system with reference to the main circuits only will first be discussed and, subsequently, the control 'circuits, by which the desired main circuit changes are accomplished, will be traced.

Assuming that it is desired to accelerate V the motor, switches LS1, LS2, S2, M2, SM2,

, ed in series relation with all-of the accelerat Q1, Q2, JR and X are first closed. With these switches closed, a circuit is established from the trolley through the coil of overload trip O.T., a main circuit conductor 1, the'switches LS2 and M2, the resistor S2, the armature M#2.', the switch SM2, control fingers 2 and 3 of the reverser which are bridged by a' contact member 4, the field magnet winding F2, control fingers 5 and 6 of the reverser which are. bridged by a contact member 7, the switch X, coils of the limit switches A1, B, C and L, resistor sections R3, R2 and R1, conductor 8, switch JR, conductor 9, resistor sections RRl RR2- and RR3, switch S1, armature Ma /:1, reverser control fingers 10 and 11 which are bridged by a contact member 12, the field magnet winding F1, reverser control fingers 13 and 14which are bridged by a contact member 15 and a conductor 16 to ground at the rail. The motors are thus connecting resistor sections included in the circuit. In the second to the eighth control steps, inclusive, the switches S2, RRl, R1, RR2,

R2, RR3, R3 are successively closed, thus gradually short-circuiting the resistor sections and connecting the motors directly in series across the line.

The next three steps effect a transition in which theswitch J is first closed, completing the temporary short-circuit connection between the field magnet winding F2 and the motor armature M#1, the switches RRl to R3, inclusive, and switch JR are next opened and the switches M1 and G are closed.

In the ninth control step, the switch J is permitted to open, leaving the two motors in parallel across the circuit, with the resistor sections R1, R2 and R3 in series with the motor M#2 and the section RRl, RR2 and RR3 in series with the motor M#1.

In the subsequent accelerating steps, the resistor sections RRl to RR3, inclusive, are short-circuited, leaving the motors in parallel relation directly across the circuit.

There are two master controller braking positions, one marked Braking and the other Holding. In operation, only the braking step will be utilized if the vehicle is to be brought to rest, but, if it isdesired only to slow down the vehicle or hold a definite speed on a down grade, the holding step may be employed.

The parallelseries regeneration step closes the switches M2, G, M1, S2, SM2, R1 and RRl and moves the PK controller from its0fi position into its position 1. By these means, the switch Xis opened and a plurality of switches Y and Z for the battery and the differential relay switch, respectively, are closed. Also the reverser is moved into its third position, whereby the two field-magnet windings are disposed in series with the ages generated at the terminals of a certain 3 motor armature and the voltage of the line, the motors are automatically connected to the line by the closing of the corresponding l1ne switches LS1 and LS2. The controller PK is thereupon automatically regulated, as

hereinafter pointed out, to so govern the field-regulating resistance as to maintain a substantially constant braking current. This obviously involves the gradual exclusion of the regulating resistance to maintain substantially constant generated voltages at the terminals of the motors as their speeds decrease.

When the vehicle speed has diminished to a. predetermined value, the transition from parallel to series relation of the motors without entirely opening the circuit is accomplished as follows: First, one regenerating armature is disconnected from the line by the opening of the LS1 switch; second, thisarally short-circuited, simultaneously with the return of the PK drum to its first position, the combined resistance-varying actions being regulated to maintain a substantially constant regenerated current. Then the PK controller, in conjunction with the exclusion of the remaining resistors,is again regulated, 1n the same manner as before, to maintain the desired braking rate as the vehicle speed decreases. In the last operative position of I the PK drum, when the vehicle has reached a realtively low speed, the air or other mechanical brakes are automatically applied to completely stop the vehicle, as hereinafter described.

It should be noted that the regenerative circuit is not entirely opened during the transition from parallel to series relation of the machines, and also that, at the same time, the maximum possible braking effort is maintained, by reason of the closure of a local braking circuit around the armature that is temporarily disconnected from the line.

In the series regeneration step, the motor armatures are initially disposed in series relation with the series-connected field windings and with certain resistors, and the motors are connected to the supply circuit when their combined voltages obtain a predetermined value. The PK controller is then automatically operated, as hereinbefore recited, to maintain a substantially constant regenerated current.

In the holding position, the actuators for the PK controller are prevented from continuing to exclude the regulating resistance and, consequently. the braking current delivered by the motors will decrease with the speed instead of continuing constant.

The PK controller is intended to be representative of anv suitable means for automatically governing the field-regulating resistance and I do not wish to .be limited to any specific control apparatus.

The controller comprisesa plurality of contact fingers 17, which are connected to intermediate points in the field-regulating resistance; suitable contact segments 18, which are adapted to successively engage the fingers 17 and gradually short-circuit the resistant in a well known manner; contact members 19 and 20, which form parts of the switch Y, and a plurality of interlocking contact members and fingers cooperatingtherewith, which will be referred to in detail in the discussion of the control circuits.

The PK controller is preferably in the form of a drum, which isshown developed into a single plane in a well-known manner, and is provided with a shaft 21 to which a pinion 22 is secured. The drum is actuated by a rack 23 which meshes with the pinion 22 and is connected, at its respective ends, to pistons 24 and 25 which operate in cylinders 26 and 27. Fluid pressure is admitted from a tank or reservoir 28, through an electro-magnetically controlled valve 29, to the cylinder 27, when an actuating coil 30 for the valve is deenergized, and fluid pressure is admitted from the tank or reservoir to the cylinder 26 when an actuating coil 31 for the other magnet valve 32 is energized.

The arrangement of parts is such that, if both magnet valves are deenergized, fluid pressure will be' admitted through the valve 29 to the cylinder 27 and will so actuate the piston 25 and the rack 23 as to throw the PK drum to its off position.

If valve magnet 32 .is energized, fluid pressure will be admitted to the cylinder 26, but no motion of the drum will result, inasmuch as the pressures are then balanced on the two sides of the piston member. A motion of the drum may, however, be roduced by subsequently energizing the 0011 30 of the valve 29, since, by this means, the valve will cut off the supply of pressure from the reservoir and will open its exhaust port. The drum may be stopped at any position by'merely deenergizing the coil 30, and it may be returned to its off position by merely. denergizing both of the coils 30 19,5 and 31.

The valve magnet 32, which, when onergized, is open to admit fluid pressure to the cylinder and, when deenergized, is closed to exhaust air from the cylinder, will here- 110 inafter be referred to as a standard valve magnet; while the valve magnet 29, which is open to admit fluid pressure to the cylin- -der when deenerg'ized and exhausts the air from the cylinder when energized, will hereinafter be referred to as an inverted valve magnet.

The reverser may be of any suitable type, but preferably comprises a drum section which, as shown, is adapted to occupy three positions, one for forward and one for reverse operation of the vehicle, designated by f and r, respectively, and a third position designated by 198, that is employed during regeneration only, whereby the field magnet windings of both motors are simultaneously reversed and connected in series relation, for

a purpose hereinafter described. The reverser is preferably pneumatically operated, and is controlledby valves having actuating coils 33 and 34 that respectively correspond to forward and reverse operation,

It should be noted that whereas, for the sake of simplicity and clearness, I have shown my reverser as adapted to permit regeneration only When the vehicle is traveling in the direction designated as forward, inasmuch as the third position ps corresponds to the forward position only of the reverser, a similar position and suitable contact members may readily be provided upon the reverser by those skilled in the 'art, to permit of regeneration in the direction designated as reverse, as will be understood.

The change-over switch COS may be of any familiar construction, preferably comprising a two-position controller of the drum type. The normal position of the switch is indicated by the legend, Acceleration and paral1el-series-regeneration, and a second position, marked Series regeneration, is employed when the vehicle is traveling at a speed which would not be suitably high to permit of the full parallelseries regenerative operation of the motors.

The limit switches Al and A1 are closed when energized above a predetermined value and the switches B, C and L are opened when energized above predetermined values.

The differential relay switch D is provided with a coil 35 which, when energized, tends to raise it, and a coil 36 which tends to hold it down.

The coil 36 is connected in shunt relation to the armature M#2, or to the series-connected armatures, according to the position of the change-over switch COS, when the PK drum occupies any of the eight shown on positions, by reason of the engagement of contact fingers 37 with a contact member 38.

The coil 35 is similarly connected across the supply circuit when the PK drum occupies positions 1 to 8, inclusive, by reason of the engagement of contact fingers 39 with a contact member 40.

"The other switches of the system are adapted to occupy two positions, one in which the main circuit is interrupted, hereinafter called the switch out position, the other in which the switch is closed and the circuit is completed, hereinafter termed the switch in position. Each of the switches is closed when its coil is energized.

The switches may be, and preferably are, actuated pneumatically, the coils respectively associated with the switches being adapted merely to open valves to admit fluid pressure to cylinders for closing the switches in a well-known manner. In fact, the construction of the main switches forms no part of my present invention, and they may be actuated directly or indirectly, in any suitable manner.

The function of the P resistors, of the (SQ-SP) and SI resistors, and of the Q, resistors may be stated as follows: The P resistors are employed in conjunction with certain of the accelerating resistors to close a temporary local circuit around one of the regenerating armatures during the transition from parallel to series relation of the motors; The (S2SP) and S1 resistors are connected in series with the armatures M #2 and M #1, respectively, during the parallel regenerating disposition thereof, to serve to steady and balance the currents delivered by the machines, that is, to prevent line surges and heavy fluctuations of current. The Q resistors are temporarily connected in circuit with one of the armatures when beginning regeneration, to balance the effect of certain other resistors in the circuit of the other parallel-connected armature.

Referring to Fig. 2 of the drawing, the control circuits here shown are governed by a master controller adapted to occupy an off position, accelerating positions 1, 2, and 3, a braking position and a holding position; and a master reverser adapted to occupy a forward position f and a reversing position 1.

Energy may be supplied to the control circuits from any suitable source, such as a control battery having a positive terminal which, together with its connected conductors, is marked 13+ and a negative terminal which, with its connected conductors, is marked 13-.

The arrangement of circuits is such that, if the master controller is moved to its position 3, the motor acceleration will progress automatically until the motors are finally connected across the line in multiple circuit relation. If the master controller is moved only to position 2, the acceleration will progress until the motors are connected across the line in full-series relation and, if the controller is moved only to position 1, the motors will be connected in series relation across the line with all of the accelerating resistors in series.

It is thus evident that automatic acceleration is provided for, but that the progression may be delayed at several points according to the will of the operator or motorman.

Assuming that the master controller is moved directly from its off position to its accelerating position'3, that the master reverser has been thrown into its position f, and that the reverser occupies its position 7', a control circuit is established from the control battery terminal and conductor 13+, through a control cut-out switch which is closed, a contact finger 41 of the master reverser, conductor 42, control fingers 43 and i l-which are bridged bya contact member 45 of the master controllerconductor 46, control fingers 47 and 48 which are bridged by a contact member 49 of the reverser, the

'switch CT. to B.

forward coil 33 thereof, conductor 50, and interlock marked M1 out, to conductor B. Another circuit is established from conductor B+ through conductor 51, control fingers 52 and 53which are bridged by a contact member 54conductor 55, interlock marked PK off, the coil of switch LS1, and a contact member of the trip relay An additional circuit is established from the conductor 55 through a second interlock marked PK off the coil of switch LS2, and as before to the conductor B. Another circuit is made from the last-named interlock PK off through a pair of similarly-designated interlocks and the coils of switches Q1 and Q2, and also through conductor 55, interlock marked PK off and the coil of the switch S1. A further circuit is completed from the conductor 55, through conductor 55, interlock marked SMl out, conductor 55 and the coil 'of switch SM2 to the negative conductor B. Thus, the reverser is thrown to its forward position 7, in which position it is shown, and the line switches LS1 LS2, Q1, Q2, S1 and SM2 are closed. The switches LS1 and SM2 are respectively connected in series with contact members of the change-over switch COS when it occupies its normal position.

In the forward position, a control circuit is established from the contact member 49, through conductor 56, coil of switch M1, and a contact member of the trip relay switch O.T. to B. Another circuit is also made from the contact member 49, conductor 57, interlock marked J-out, conductor 58, interlock marked M2out, interlock marked PK ofi, and the coil of the switch JR to a negative conductor 59, circuit being completed as before. Thus, switches M1 and JR are closed as soon as the reverser and the master reverser occupy corresponding positions.

The closing of these switches connects the motors in series relation, with various resistor sections included, as above indicated. The current traversing the motor circuit is suflicient to raise the limit switch L in a well-known manner. As soon as the limit switch is again closed, by reason of the increased speed and counter-electromotive force of the motor armatures, another control circuit is established from the energized contact member 54 of the master controller, through conductor 60, limit switch L, interlock marked M1 in, interlock marked JR in interlock marked PKofi", conductors 61 and 62, corresponding contact members SPout and S2out and the coils of switches SP and S2 to conductor 59. The switches SP and S2 are thus closed, their coils being transferred, in a well-known manner, from the actuating circuit just described to a holding circuit established through conductor 63, and conductor R to the interlock marked J-out. The actuating circuit, which was completed through the coil of the switch SP, is now com leted through contact member SP in, con uctor 64, contact member RRl out and the coil of the switch RRl. The actuating circuit is not completed, however, until the limit switch L is again closed, provided the rush of current in the main circuit, produced by the exclusion of the resistor S, has been sufiicient to open the switch.

Similarl the coils of the switches R1, RR2, R2, R3, and R3 are successively energized and transferred in multiple relation to a holding circuit embracing the conductor 58.

As soon as the R3 switch is closed, a circuit is completed from the energized contact member 54 of .the master controller through conductor 65, interlock marked R3 in, conductor 66, interlock marked G out, conductor 67 and the coil of switch J to the conductor 12, thereby closing the switch J to complete the main bridging circuit hereinbefore referred to. In closing, the switch J actuates the interlock marked J to the in" position to interrupt the supply of energy to the holding conductor 58, thus permitting the resistor switches RRl to R3, inclusive, and the switch JR to open. lVith the switch JR open, a circuit is established. dependent upon the limit switch L, through interlock marked M1 in, conductor 68, interlock marked JR out, conductor 69, and the coils of the switches M2 and G to conductor 59. \Vhen the switch G is closed, the circuit through the coil of the switch J is interrupted at the interlock marked G out and, consequently, switch J is opened and the motors are connected in multiple circuit relation, the resistor section R1, R2 and R3 being included in series with the motor M#1, and the resistor sections RR1, RR2 and RR3 being included in series with the motor M#2.

It will be observed that the holding circuit of the switches SP -and S2 is independent of the position of the switch J and, consequently, these switches remain closed during the complete accelerating operation of the controller, after they have once been actuated.

The resistor sections are again short-circuited, dependent upon the limit switch L, a substantially balanced relation being maintained between the circuits of the two motors by reason of the fact that the switches, which close in succession, are selected alternately from the two groups. The switch JR remains 0 en on account. of the interlock marked 2 out, which makes it imossible to close both the switches JR and 2 at one time. This is particularly important, since the switch JR will short-circuit the line if it is closed when the switches M1, M2 and G are closed.

Referring now to the regenerative connectlons and assuming that the motor-propelled vehicle is operating at or above a predetermined rate of speed and that the master controller has been returned to its ofi' position, permitting all of the switches to open, and is moved to its braking position, the change-over switch COS occupying its normal position; under these conditions, energy is supplied from control finger 70 of the master reverser, through the conductor 42, control fingers 43 and 73-which are bridged by a contact member 74 of the master controllerconductor 75, control fingers 76 and 7 7-which are bridged by a contact member 78 of the reverserconductor 79 and the reversing coil 34 of the reverser. By reason of the relatively great length of the contact member 78, the reverser, without manipulation of the master reverser, is moved to its third position marked 798, thereby reversing the two field magnet windings, for a well-known purpose, and connecting the parallel-disposed armatures in series relation to the series-connected field magnet windings, as described below.

lVhen the reverser occupies its third position, the main circuit connections are as follows, the circuits, however, not being completed at this time: from the trolley to conductor 1, where the circuit divides, one path including switches LS2 and M2, armature l\'l#2, switch SM2, control finger 2 of the reverser which engages a contact member 80, and a conductor 81, the other path including switchesLSl and M1. armature M#1, control finger 10 of the reverser which engages a contact member 82, and the conductor 81. A field conductor 83 joins the common armature conductor 81 to a contact member 84 which makes contact with the control finger 13, whence circuit is continued through the field magnet winding F1 in the reversed direction, control finger 11 which engages a contact member 85, conductor 86, contact member 87 which makes contact with the control finger 5, the field magnet winding F2 in the reversed direction, the control finger 3 which engages a contact member 88, conductor 89, the control finger 6, the field-regulating resistance FR, the limit switches A1, B, C and L and the switch G to the rail.

Another preparatory control. circult is established from the energized control finger 52 of the master controller, through a contact member 90 and control finger 91 thereof, conductors 92 and 93, interlock marked S2 out, and conductor 94, to control fingers 95, 96 and 97 which are bridged by a contact member 98. The fingers 96 and 97 are connected by conductors 99 and 100 to the inverted valve magnet and the standard verted valve magnet coil 30 is interrupted,

and the circuit through the standard valve magnet coil 31 is maintained, by reason of the peculiar shape of the contact member 98. Full pressure then obtains in both cylinders 26 and 27 and, consequently, the controller remains in position 1.

Energy is also supplied from contact member 74 of the master controller, through a. control finger 101, conductor 102, control fingers 103 and i04-which are bridged by a contact member 105 of the reverser, in the third position thereof-and the conductor 56 to the coil of the switch M1 which is, consequently, closed. A circuit is also made from the finger 104, through conductors 57 and R, interlock marked PKl to 8, and conductor 69 to the coils of the switches M2 and G. Upon the closure of these two switches, a circuit is established from the conductor R, through interlock marked G in, the conductor 68, interlock marked M2 in and the conductor 61 to the coil of the switch SP.

The switch SP then closes and energy is sup-plied successively 'to the coils of the switches RRl and R1. The resistor sections SP, RBI and R1 are thus short-circuited. The closure of the switches will not proceed as in the case of acceleration from RRl to R3, inclusive, by reason of the contact member marked PK off, which is introduced in the circuit between the auxiliary contact members of the switches R1 and BB2. At this stage of the control operation, it will be observed that the armature M#2 and resistors (S2SP), Q1 and Q2 are disposed in parallel with the armature M#1 and re sistors S1, RR2, and RR3, and the resistors R2 and R3 are connected in the series field main circuit.

As soon as the PK controller assumes its first on position, the two field magnet windings and the resistance FR are bridged by the battery SB, since the switches Y are closed in this position.

The storage battery serves to excite the field magnet windings, and, inasmuch as the vehicle is assumed to be operating above a predetermined rate of speed, the motors will act as generators the voltages of which are dependent upon the speed and field strength.

'VVhen the circuits are in the condition just described, however, the generated electromotive forces are somewhat lower than the electromotive force of the supply line and, consequently, the differential relay switches remain down. 4

Upon the occupation of position 1 by the ,tion clutch connection.

PK controller, a circuit is established from conductor 92, through conductor 106, interlock marked PK1 to 8, differential relay contact members marked D down, conductor 107, limit. switch contact members marked B down, conductor 108, interlock marked LS2 out, conductor 109, the inverted valve magnet coil of the PK controller, conductor 110, control fingers 111 and 112which are bridged by a contact member 113 of the master controllerand conductors 114 and 115 to the negative side of the control battery. The standard PK valve magnet, also is energized from conductor 107, through conductor 116, interlock marked LS2 out, limit switch contact members marked C down, conductor 117, the coil of the standard valve magnet,- and conductor 118 to the conductor B--.

As'soon as both of the PK controller magnets are energized, the controller will move from its first positions, through its second, third, fourth, etc., gradually excluding the field-regulating resistance FR from the circuit until the voltage generated at the terminals of the motor armatures reaches a predetermined value, which is in excess .of the line voltage at least by an amount equal to the battery voltage, when the differential relay switch D will be raised. Thereupon, the circuits just traced through the magnet coils of the PK controller are temporarily interrupted, and a new. circuit is established from conductor 92, through the interlock marked S2 out, difi'erentlal relay contact members marked D up, interlock marked PK1 to 8, conductors 119 and 155, interlock marked AIin which is associated with and operated by an air-actuated valve AI, as hereinafter described, conductor 156, and the coil of switch LS2 to the conductor B. A companion circuit is established fromconductor 119, through conductor 120, Interlock marked PK1 to 7, and conductor 121 to the coil of the switch LS1. The line switches LS1 and LS2 are thus closed and the motors are connected to the supply circuit through the various resistor sections hereinbefore specified? Upon the raising of the D switch and the consequent above-mentioned interruption of the two valve-magnet circuits, the PK controller moves toward its off position, in a manner hereinbefore explained. The amount of backward movement is determined by a stationary stop 122 that adjust-ably engages a slip-segment 123 which is associated with the PK drum by a fric- The arrangement of parts is such that a predetermined backward movement of the drum is produced, irrespective of its position when the differentlal relay switch is raised, until the contact segment 123, in conjunction with an interlock marked SM2 in, bridges the gap in the circuit of the standard valve magnet that was made by the removal of the interlock marked LS2 out when the switch LS2 closed. The other gap in the circuit, namely, that at the contact members marked D down is closed, as soon as the switch LS2 closes, by an interlock marked LS2 in. The standard valve magnet coil is thus energized, and the PK controller is held balanced in a certain position. It should be noted that the contact segment 123 is sufliciently wide to bridge the distance between the off position and position 1, thereby preventing the PK controller from dropping back beyond its first on position, which would entail the opening of the line switches. A permanent holding circuit subsequently replaces the contact segment 123, as hereinafter pointed out.

The backward movement of the PK drum reinserts a certain amount of the field regulating resistance FR, just at the time when the motors are connected to the line. This is particularly important, because the direction of current in the battery is immediately changed, since it is connected in series relation to the motor armatures, by the braking current. The battery voltage is, therefore, suddenly raised, and the field magnet windings are very much strengthened, and tend to suddenly increase the braking current. Just sufiicient field-regulating resistance, however, is reinserted to avoid excessive rush of current and excessive armature voltage. It is evident from the foregoing that the battery holds the field current substantially constant and either supplies energy to the field or absorbs the difference between the field current and the armature currents in effecting this regulation. Since the battery is being charged during a part of the time it is in o eration, its capacity may be relatively sma 1.

After the closure of the line switch LS2, when the current has dropped to a value suflicient to permit the limit switch B to assume its lower position, a circuit is established from conductor 108 through an interlock marked LS2-in, conductor 124, interlock marked PK1 to 8, conductor 125 and the coil of switch BB2. The switches RR2, R2, BB3 and R3 are successively closed, as hereinbefore described, dependent upon the limit switch B. In addition, the

coil of Q1 is energized from interlock of load between the motors. The resistors (S2SP) and S1, however, remain in circuit for a purpose .hereinbefore specified.

The closure of the R3 switch closes the above-mentioned holding circuit for the standard valve magnet, by means of an interlock marked B3 in which is disposed in series with an interlock marked Pl out to bridge the contact members marked SM2 in and 123. Also, another circuit is 1 established from an interlock marked B3 in, through conductor 130, contact member 130 of the change-over switch, interlock marked PK1 to 8, conductors 131, interlock marked P1 out, conductor 132, interlock marked LS2in, and conductor 109 to the inverted valve magnet of the PK controller.

' The inverted valve magnet is thus energized whenever the limit switch Bl is closed and, consequently, a series of forward movements of the PK controller occurs, thereby reducing the field-regulating resistance PB and keeping the regenerated current above a predetermined lower value. The abovedescribed regenerative circuits are diagrammatically illustrated in Fig. 3.

If the braking current should exceed a predetermined higher value, when the B3 switch is in, the limit switch C will open and will suddenly bring the controller to rest. This action is effected by contact segment 133 which is connected in shunt to the auxiliary contact members of the limit switch C. The segment is restricted to a very small movement by a stationary stop 134 and is connected to the drum by a friction clutch connection, the arrangement of parts being such that it requires a very small backward movement of the drum to reestablish a balanced condition between the pressures in the cylinders 26 and 27.

Thus, it is evident that the limit switches B and C hold the braking current within predetermined values, irrespective of the speed at which the motor is operated.

The forward movement of the PK controller will continue until position is reached, when the. circuit'of the coil of switch LS 1 is broken at the interlock marked PK-l to 7.

Thereupon a circuit is made from the conductor 116,through contact member 116 of the change-over switch 7, through inter locks marked, respectively, SM2 in LS1 out,' and B3 in the coil of switch SMl, conductor 135, and the conductor 118 to the negative conductor B.

SMl is thus closed and actuates' an interlock marked ,SMl in which bridges the three series-connected interlocks just recited to form a holding circuit; p

The closure of the switch SMl disposes a local braking circuit including the re- The switch.

sisters P1, P2, P3 and S1 around the armature M#1, the circuit being as follows: from one terminal of the armature M#1, through the resistor S1, the switches BB3, BB2 and BB1, the resistors P1, P2 and P3, conductor 136, the coil of the limit switch A2, the

, switch SMl, conductors 137 and 138,- the switch SM2, the control finger 2 and the contact member of the reverser, the conductor 81, the contact member 82, and the control finger 10 to the other side of the armature M# 1. The rush of current through the new main circuit raises the limit switch A2, thus, in conjunction with an interlock marked SM2-in serving to temporarily maintain the circuit of the SM2 switch coil, the original circuit having been broken at the interlock marked SMl out, which is bridged by the limit switch A2 contact mem-' bers and the said interlock SM2 in. The main circuits just described are diagrammatically shown in Fig. 4.

When the current in the local braking circuit has assumed a steady predetermined value, the limit switch A2 drops, and the switch SM2 opens and cannot again be closed through the raising of the limit switch A2, by reason of the exclusion from its auxiliary circuit of the interlock SM2 in When the switch SM2 opens, a circuit is established from the conductor 116, through interlocks marked, respectively, SM2 out and PK-1 to 8 conductor 139, and the coil of the switch P1 to the conductor 135.

As soon as the P1 switch closes, the circuits of both the inverted and the standard magnet valve coils are interrupted at the corresponding interlocks marked P1 out, "thereby again permitting the controller to run backward. However, the movement is notstopped as early as before, since the slip segment 123 is rendered inoperative in this case by reason of the series connection therewith of the interlock marked SM2 in The movement is halted by the energization of thestandard valve magnet through an interlock marked S1 in, which bridges the open interlock marked P1 out, when the S1 switch closes, as described below.

The closure of the P1 switch causes the switches P2 and P3 to close successively, the switch coils being transferred upon actua- "tion of the switches to a holding conductor 140 which is connected to the conductor 116. When the P3 switchis closed, a circuit is 120 established from an interlock marked P3i'n, through a conductor l llto the coil of the switch S2. As soon as the switch S2 closes, a circuit is made from the cons, ductor 55 through an interlock marked S2 .125 in, to lthe coil of the switch S1. At this stage of the control operation, therefore, all the resistor sections are short-circuited and i the motors are disposed in full-series relation. It will be noted that the transition from parallel to series-circuit relation of the motor armatures is continuous, that is, a continuously regenerated current is maintained throughout the. transition. The design and arrangement of parts is such that the PK controller will run back to, but not beyond, position 1 by the time the switch S1 closes, which closure energizes the standard valve magnet and stops the controller. Since the field-regulating resistance FR is thus being inserted in circuit while the various resistor sections are being excluded, a substantially constant braking current is maintained.

Fig. 5 shows diagrammatically'the main circuit changes just described.

The closure of the S1 switch also causes a bridging of the open interlock marked P1 out in the circuit of the inverted valve magnet by an interlock marked S1-in. The PK controller, therefore, again moves forward, dependent upon the limit switch B, to gradually exclude the field regulating resistance FR and maintain a substantially constant regenerated current. The main circuit connections just, described are diagrammatically illustrated in Fig. 6.

When the PK controller occupies its position 8, a circuit is established from the energized finger 91 of the master controller, through the contact member 90, control finger 142, conductor 143, interlock marked PK-8, conductor 144, and a coil 145 of a relay switch 146 to the conductor B. When the switch is closed, a holding circuit is established from the conductor 143 to the conductor 144 through an upper pair of contact members 147 of the switch 146.

A lower pair. of contact members 148 are also bridged upon the closure of the switch,

and they complete a circuit from the con-v ductor 13+ to the conductor B through a coil 149 of a magnet valve 150. This valve, when energized, closes an exhaust port 151 and opens an admission port 152,

thereby admitting pneumatic pressure from a tank or reservoir 153 to a'brake cylinder 154. The cylinder and valve shown are intended to represent any well-known system of pneumatic brakes which may be independently controlled in the usual manner ut which are automatically applied when the PK controller occupies its position 8.

It will be observed that the circuit through conductor 143 is broken when the master contr 'ller is returned to either its holdingor its off position. Simultaneously with the actuation of the braking apparatus, fluid pressure is also ad- .mitted to the air-actuated valve AI, whereby the valve is actuated and the control circuit of the line switch LS2 is broken at the associated interlock, thus opening the reg'enerative circuit. The opening of the switch LS2 entails the opening of the circuits of both valve magnets of the PK controller at the interlock marked LS2 in thereby causing the drum to return to its off position. The air brakes will not be released, however, while the master controller occupies its braking position. v

The holding position of the master controller difiers from the braking position only in that the circuit of the inverted valve magnet coil is interrupted at the contact member 113 of the master controller. this means, the progression of the PK controllers may be arrested at any point and thereby cause the speed of the vehicle to decrease more slowly, or to continue at a constant speed if it is traveling down hill. The operator is thus enabled, by moving his controller from one position to the other,

" to regulate the rate of retardation or to hold regeneration, after the return of the master controller to the off position, and the controller ma then be moved to its braking position. nder these conditions, the reverser is automatically actuated to its reverse position,' as hereinbefore described. The motor armatures are thus disposed in series relation with the reversed field ma'gnet windings, since the main circuits throu h the switches LS1 and SM2 are broken in the change-over switch, and the switch SMl is bridged by a contact member thereof. Likewise, the switch S2 is bridged by a similar contact member, the circuit insertion of the corresponding resistors not being necessary in the present operation.

The main circuit connections are thus as follows, the circuits, however, not bein completed at this time: from theftrolley, through conductor 1, switches LS2 and M2, short-circuited switch S2, armature M 2, short-circuited switch SM1, resistors 3, P2,.P1 and RRl, BB2, BB3, switch S1, armature Miil, and the reverser and field magnet-windings, as described in connection with parallel-series regeneration.

The valve magnets of the PK controller are energized from conductor 93, through a contact member 93 of the change-over switch which bridges the interlock S2 out, conductor 94, and thence as hereinbefore set forth. The PK controller thus occupies its first on position, with the battery SB bridging the field magnet windings and the field-regulating resistor FR. The switches M2, G, RRl and R1 are also closed; and the PK controller is automatically regulated to increase the voltage generated at the motor terminals, in the manner hereinbefore described, until the voltage across the combined motor armature reaches a predetermined value, when the differential re ay switch will be raised to effect regenerative connection of the motors to the supply circuit. Fig. 5 represents the main circuit connections at this time. The PK controller is returned toward its off position, upon the completion of this connection; and the resistor switches BB2, R2, BBB and R3 are successively closed, dependent u on the limit switch B, as hereinbefore set orth.

The actuating coils of the P switches are then successively energized from conductor 130, through contact member 130 of the change-over switch and conductor 139. The main circuit resistors are thus all excluded from circuit to maintain a substantially constant regenerated current, before the PK controller is again operated.

The PK controllermagnet coils are energized after the closure of the P3 switch, from a contact member 155 thereof, conductors 141 and 156, contact member 157 of the change-over, switch, conductors 158 and 130, and thence as described in connection with parallelseries regeneration. However, when the PK controller reaches its seventh position, the controller is not returned toward its off position with the concurrent operation of switches, as set forth relative to parallel-series regeneration,

' by reason of the bridging of the interlock and PK1 to 8.

PK-1 to 7 by the series-connected contact members 159 of the change-over switch, The PK controller thus continues to its eighth and last position, in accordance with the value of armature current. The air brakes are then automatically actuated, as hereinbefore described. It is believed that the foregoing description, in

view of the full account of parallel-series regeneration, is suificiently extensive to enable those skilled in the art to fully understand the straight series regenerative feature of my invention.

Independently operated switches may be substituted, as hereinbefore indicated, for the PK controller, and it may be found desirable to utilize entirely separate resistors and, in some cases, separate line-switches for governing the braking connectigns, as distinguished from the accelerating connections of the system.

It will be understood that; if'the supplyircuit voltage remains substal ti'a lly confield-regulating resistor.- However, if the.

supply. circuit voltage fluctuates considerably, as is usually unavoidable in trolley circuits of the class in question, then the direction of movement of the PK controller is governed by the relative values of the variations in voltage between the regenerated and the supply circuit voltages.

The circuit connections and the arrangement of the apparatus may, of course, be varied within the spirit and scope of my invention. The invention is, for example, not limited to a two-motor controller, nor to a system having any specific arrangement of switches or motors; and I, therefore, desire that only such limitations shall be imposed as are indicated in the appended claims.

\ I claim as my invention:

1. In a system of control, the combination with a supply circuit, and a plurality of electric motors severally havin armature windings and field magnet wlndings, of means for connecting the motors to the supply circuit to return energy thereto, with certain windings of the respective motors connected in parallel-circuit relation and the remaining windings in series-circuit relation to said parallel circuit.

2. In a system of control, the combination with a supply circuit, and a plurality of electric motors severally having armature windings and field magnet windings, of means for connecting the motors to the supply circuit to return ener' thereto, with the armature windings o the respective motors connected in parallel-circuit relation and the field magnet windings in seriescircuit relation to said parallel circuit.

3. In a system of control, the combination with a supply circuit, and a plurality of electric motors severally havin armature windings and field magnet wlndings, of

motors connected in parallel-circuit relation and the remaining windings in series-circuit relation to said parallel circuit and for subsequently connecting said certain windings in series-circuit relation to said remaining windings.

4. In a system of control, the combination. with a supply circuit, and a plurality of electric motors severally having armature windings and field magnet windings, of means for connecting the motors to the supply circuit to return energy thereto, with the armature windings of the respective motors connected in parallel-circuit relation and the field magnet windings in seriescircuit relation to said parallel circuit untll a predetermined motor speed is attained and for then connecting said armature windings in series-circuit relation to said field magnet windings while maintaining a continuously regenerated current.

5. In a system of control, the combination with a supply circuit, and a plurality of electric motors severally having armature windings and field magnet windings, of automatic control means for connecting the motors to the supply circuit to return energy thereto, with the armature windings of the respective motors connected in parallel-circuit relation until a predetermined speed is attained, and for then connecting said armature windings in series-circuit relation while maintaining a continuously regenerated current.

6. In a system of control, the combination with a supply circuit, and a plurality of electric motors severally having armature windings and field magnet windings, of automatic control means for initially connecting the motors to the supply circuit to return energy thereto, with certain windings of the motors connected in parallel-circuit relation, and the remaining windings in series-circuit relation to said parallel circuit and for subsequently connecting said certain windings in series-circuit relation to said remaining windings.

7. In a system of control, the combination with a supply circuit, and a pluralityof electric motors severally having armature windings and field magnet windings, of automatic control means for connecting the motors to the supply circuit to return energy thereto, with the armature windings of the respective motors connected in parallel-circuit relation, and the field magnet windings in series-circuit relation to said parallel circuit until a redetermined motor speed or maximum fiel strength is attained, and for then connecting said armature windings in series-circuit relation to said field magnet windings until a relatively low speed is attained.

8. In a system of control, the combination with a supply circuit, a plurality of electric motors severally having armature windings and field magnet windings, ofan auxiliary source of energy, a field-regulating translating device adapted to be connected in series with said source of energy and said field magnet windings for excitation thereof, of automatic means for connecting the motors to the supply circuit to return energy thereto, when a predetermined voltage relation exists between the motor armatures and the supply circuit, certain windings of the respective motors being disposed in parallel-circuit relation, and interlocked switching means for subsequently automatically connecting said certain windings in series-circuit relation.

9. In a system of control, the combination with a supply-circuit, a plurality of electric motors severally having armature windings and field magnet windings, of a field-regulating resistance that is normally short-circuited when the motor is in operation and is adapted to be connected in circuit with the field magnet windings, of an auxiliary source of energy, means for introducing the field-regulating resistance, connecting the auxiliary sourceof ener across the field magnet windings and said resistance, automatic means for connecting the motor to the supply circuit to return energy thereto and to retard the motors when a predetermined voltage relation exists between the motor armatures and the supply circuit, the armature windings of the respective motors being disposed in parallel-circuit relation and means for subsequently connecting said armature windings in series-circuit relation.

10. In a system of control, the combination with a, supply-circuit, a plurality of electric motors severally havin armature windings and field magnet win ings, of a field-regulating resistance that is normally short-circuited when the motor is in operation and is adapted to be connected in series with the field magnet windings, of an auxiliary source of energy, means for in troducing the field-regulating resistance and connecting the auxiliary source of energy across the field-magnet windings and said resistance, automatic means for connecting the motor to the supply circuit to return energy thereto and to retard the motors when ya predetermined voltage relation exists between the motor armatures and the supply circuit, the armature windin s of the respective motors being dispose in mutually parallel-circuit relation and in common series-circuit relation to the field-magnet windings, and means for subsequently connecting said armature windings in series-circuit relation to each other and to said field-magnet windings while maintaining a continuously regenerated current.

11. In a control system, the combination with a plurality of motors, of interlocked switching means for automatically accelerating said motors and for automatically establishing a regenerative circuit wherein the respective motor armatures are initially disposed in parallel-circuit relation and subsequently in series-circuit relation while maintaining said regenerative circuit.

12. In a control system, the combination with a supply circuit, a plurality of serieswound electric motors, a storage battery, a field-regulating resistance, and means for connecting the storage battery in shunt-circuit relation to the field magnet windings and said resistance, of automatic means for connecting the motors to the supply circuit when the voltage generated at the armature terminals bears a predetermined relation to the supply-circuit voltage, the armature windings of the respective motors being initially disposed in parallel-circuit relation, and means for subsequently connecting said armature windings in series-circuit relation while maintaining a substantially constant regenerative current. I

13. A control system comprising a sup ply circuit, a plurality of electric motors,

\ interlocked switching means for successively arranging the motors in a series and in a parallel-circuit relation for accelerating the motors, for establishing a regenerative braking circuit embracing an initial parallel and a subsequent series-circuit relation of the motor armatures, and means for maintaining substantially constant braking currents as the motors are retarded.

14. A- control system comprising a supply circuit, a plurality of series-wound electric motors, and means for either connecting-the motors successively in a series and in a multiple-circuit relation for accelera tion, or-initially connecting the motors to the supply circuit for returning energy thereto and with the armature windings in mutual parallel-circuit relation and in common series-circuit relation with the field magnet windings, and subsequently disposing the armature windings in mutual seriescircuit relation while maintaining substantially constant braking currents as the motors are retarded.

15. A control system, comprising a plu-- rality of electric motors severally having armature windings and field-magnet windings, control means for efi'ecting the acceleration of the motors, other control means for regulating the field excitation of the motors and severally connecting them to the supply circuit to return energy thereto, with said armature windings initially in parallelcircuit relation, and further control means for subsequently disposing said armature windings in operative series-circuit relation.

16. In a control system, the combination with a plurality of electric motors severally having armature windings and field magnet windings, control means for effecting the acceleration of the motors, other control means for regulating the field excitation of the motors and. severally connecting them to the supply circuit to return energy thereto, with the armature windings initially in parallel-circuit relation, and further -control means for subsequently disposing'sai'd armature. windings in series-circuit relation, vof a single means for means. i

17 In a control system, the combination with a plurality of electric motors severally having armature windings and field magnet windings, control means for effecting the acceleration of the motors, other control governing all the control,

means for regulating the field excitation of the motors and severally connecting them to the supply circuit to return energy thereto, with the armature windings initially in parallel-circuit relation, and further control means for subsequently disposing said armature windings in series-circuit relation, of a master controller adapted to govern one of said control means when adjusted in one direction and to govern the other control means when adjusted in another direction.

18. In a control system, the combination with a plurality of electric motors severally having armature windings and field magnet windings, control means for effecting the acceleration of the motors, other control means for regulating the field excitation of the motors and severally connecting the-nito the supply circuit to return energy thereto, with the armature windings initially in parallel-circuit relation, and further control means for subsequently disposing said armature windings in series-circuit relation, of a master controller for governing the aforesaid control means, one of said control means embodying differential relay switches dependent upon a predetermined voltage relationvbetween the supply circuit and the motor armatures for connecting the motors to the circuit to return energy thereto.

19. In a control system, the combination with a supply circuit, a plurality of electric motors severally having armature windings and field-magnet windings and a field-regulating resistance, of an auxiliary supply circuit adapted-to be connected across the field-magnet windings and the regulating resistance, a differential relay switch dependent upon a predetermined voltage relation between the supply circuit and the motor armatures for connecting the motor to the supply circuit to return energy thereto, with the respective armature windings initially connected in parallel-circuit relation,

ion

and interlocked switching means for subseresistance, means for initially connecting the respective armature windings in parallel-circuit relation and subsequently in series-circuit relation to return. energy to the line",,and a master controller adapted to occupy one series of positions for governing the accelerating control means and another set of positionsfor governing the other corp. trol means.

21. A control system comprising a supply circuit, a plurality of electric motors severally having armature and field magnet windings, a field-regulating resistance, an auxiliary source of energy, a differential relay switchdependent upon a predetermined relation between the supply circuit voltage and the voltage across the terminals of the armatures for regeneratively connecting the motor to said supply circuit initially, with the respective armature windings in parallel-circuit relation and subsequently in series-circuit relation, and a master controller adapted to occupy one set of control positions for governing the acceleration and operation of the motor and another set of control positions for efiecting the intrduc tion and control of the field-regulating resistances, the excitation of the field-magnet windings from the auxiliary source, and the said regenerative connections of the motor, said last-named connections being initially directly dependent upon the difi'erential relay switch.

22. A system of control comprising a supply circuit, a plurality of series motors severally having armatures and field magnet windings, means for simultaneously regulating the field magnet windings, a' storage battery connected in shunt-circuit relation to the field magnet windings and the regulating means and adapted to receive energyv from, or deliver energy to, the field circuit, according as the armature current is greater or less than the field currents.

23. A system of control comprising a supply circuit, a plurality of series motors severally having armature and field-magnet windings, means for regulating the fieldmagnet windings, a storage battery adapted to receive energy from, or deliver energy to,

the field circuit, according as the armature current is greater or less than the field cur rent, and means for connecting the motors to the supply circuit to return energy thereto initially, with the respective armature windings inv parallel-circuit relation and subsequently in series-circuit relation.

24. A system of control comprising a supply circuit, a plurality of series. motors severallyhaving armatures and field-magnet windings, a resistance connected in series I with the field-magnet windings, a storage battery connected in shunt relation to the field windings and the resistance and adapted to receive energy from the motor circuit or to supply energy to the field-magnet windings, according as the armature cur rent is greater or less than the field current when the motors are connected to the supply circuit for returning energy thereto initially, with the armature windings in parallel-circuit relation and subsequently in series-circuit relation. 25. A system of control comprising a supply circuit, a plurality of series motors severally having armatures and field-magnet windings, a resistance connected in series with the field magnet windings, means for connecting the motors to the supply circuit to return energy thereto during the braking period, with the armature windings initially connected in parallel-circuit relation and subsequently in series-circuit relation, means for regulating the resistance, a storage battery connected in shunt relation to the field windings and the resistance and adapted to receive energy from the motor circuit or to supply energy to the field magnet windin'gs, according as the armature current is greater or less than the field current.

26. A system of control comprising a plurality of series motors severally having armature and field magnet windings, a mechanical brake apparatus, means for connecting the motors to the supply circuit to return energy thereto, with the respective armature windings initially in parallelcircuit relation and subsequently in seriescircuit relation, means for regulating the excitation of the field, and means automatically dependent upon the regulating means for actuating the mechanical brake apparatus.

27. A control system comprising a supply circuit, a plurality of series motors severally having armatures and field-magnet windings, a mechanical brake apparatus, an auxiliary source of energy, and regulating means for gradually strengthening the motor fields to maintain a substantially constant braking current and to return energy to the supply circuit, with the arma-' ture windings initially in parallel-circuit relation and subsequently in' series-circuit relation, and means dependent upon the field-regulatng means for automatically actuating the mechanical brake apparatus.

28. Acontrol system comprising a supply circuit, a plurality of series motors severally having armatures and field-magnet windings, a mechanical brake apparatus, means for regulating the field-magnet windings, a.

chanical brake apparatus.

29. A control system comprising a supply circuit, a mechanlcal brake apparatus, a plurality of series motors adapted to return ener to'the supply circuit, means for gradual y strengthening themQtOr fields and for aeeaees initially connecting the armatures in parallel-circuit relation and subsequently in series-circuit relation as the motor speed is reduced, and automatic means dependent upon said field-regulating means to actuate the mechanical brake apparatus.

30. A system of control comprising a supply circuit, a plurality of series motors severally having armatures and field-magnet windings, a mechanical brake apparatus, a resistance connected in series with the fieldmagnet windings, means for connecting the motor to the supply circuit to return energy thereto, with the respective armature windings initially in parallel-circuit relation and subsequently in series-circuit relation, means for regulating the resistance, a storage battery connected in shunt relation to the field windings and the resistance and adapted to receive energy from the motor circuit or to supply energy to the field magnet winding, according as the armature current is greater or less than the field current, and automatic means dependent upon the resistance-regulating means for actuating the mechanical brake apparatus.

' 31. In a control system, the combination with a plurality of series wound electric motors, a mechanical brake apparatus, and

means for establishing a regenerative braking circuit, with the respective armature windings initially in parallel-circuit relation and subsequently in series-circuit relation and maintaining a. substantially constant braking current as the motor is retarded, of means for automatically actuating the mechanical brake apparatus at a predetermined point in the retardation of the motor.

32. A system of control for braking electric motors comprising a supply circuit, a

plurality of motors severally having armatures and field magnet windings, a variable resistance, an auxiliary source of current, means for connecting the said source and said resistance in circuit with the field-magnet windings, means for regulating the said variable resistance in accordance with the current and electromotive force generated by the motor armature, and means for connecting the motors to the supply circuit, with the respective armatures initially in parallel-circuit relation and subsequently in series-circuit relation, said initial coimection occurring when the voltage generated by the motor armatures attains a predetermined value.

33. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having seriesconnected armatures and field magnet windings, a variable resistance, an auxiliary source of current, means for connecting the said source and said resistance in circuit with the field magnet windings, means for @automatically regulating the said variable resistance in accordance with the current and electromotive force generated by the motor armatures, means for automatically connecting the motor to the supply circuit, with the res ective armature windings in parallel-circuit relation when the voltage generated by the motor armatures attains a predetermined value, and means for subsequently connecting said armature windings in series-circuit relation.

34. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field-magnet windings, a variable resistance, an auxiliary source of current, means for connecting the said source and said resistance in circuit with the field-magnet windings, means for automatically connecting the motors to the supply circuit, with the respective armatures in parallel-circuit relation when the voltage generated by the armatures attains a predetermined value, means for subsequently connecting said armatures in series-circuit relation, means for regulating the said variable resistance, and means controlling said regulating means, whereby the current generated by the motor armatures is maintained in excess of a predetermined value until the motor speed has diminished below a predetermined value dependent upon the concurrent value of the voltage of the supply circuit.

35. A system of control for braking elec tric motors comprising a supply circuit, a plurality f motors severally having armatures and field-magnet windings, a variable resistance, an auxiliary source or" current, means for connecting the said source and said resistance in circuit with the field magnet windings, means for automatically connecting the motors to the supply circuit with the respective armature windings in parallel-circuit relation when the voltage generated by the motor armatures attains a predetermined value, means for subsequently i connecting said armatures in series-circuit relation while maintaining a continuously regenerated current, means for regulating the said variable resistance, and means controlling said regulating means, whereby the current generated by the motors is maintained between predetermined values until the motor speed has diminished below a predetermined value dependent upon the concurrent value of the voltage of the supply circuit.

36. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field-magnet windings, a variable resistance, an auxiliary source of current, means for connecting the said source and said resistance in circuit with the field-magnet windings, means for automatically connecting the motors to the supply, circuit,

with the respective armatures in parallelcircuit relation when the voltage generated by the armature attains a predetermined value, means for subsequently connecting said armatures in operative series-circuit relation, and means for regulating the said variable resistance to maintain the current generated by the motor armatures in excess of a predetermined. value until the motor speed has diminished below a predetermined value, dependent upon the concurrent value of the voltage of the supply circuit.

37. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field magnet windings, a variable resistance, an auxiliary source of current, means for connecting the said source and said resistance in circuit with the field-magnet windings, means for automatically connecting the motors to the supply circuit, with the respective armatures in parallelcircuit relation when the voltage generated by the motor armatures attains a predetermined value, means for subsequently connecting said armatures in operative seriescircuit relation, and means for regulating the said variable resistance to maintain the current generated by the motor armatures between predetermined values until the motor speed has diminished below a predetermined value dependent upon the concurrent value 0 the voltage of the supply circuit.

38. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field magnet windings, a variable resistance, an auxiliary .source of current, means for connecting the said source and said resistance in circuit with the field magnet windings, means for automatically connecting the motors to the supply circuit, with the. res ective armature windings in parallel-circuit relation when the voltage generated by the armatures attains a predetermined value, means for subsequently connecting said armatures in operative series circuit relation, a controller for said variable resistance, means for actuating said controller to increase or decrease the effective value of said resistance, and means for controlling said actuating means, whereby the efi'ective value of the said resistance is reduced when the current generated by the motor armatures diminishes below a predetermined value and whereby the efiective value of said'resistance is increased when the current generated by the motor armatures exceeds a predetermined value.

39. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field-magnet windings, an auxiliary source of current, means for connecting cuit relation and subsequently in series-cirn cuit relation, and means for regulating the current in the field magnet windings of the motors to maintain the current generated by the armatures between predetermined values until the motor speed diminishes below a predetermined value.

40. A system of control for braking an electric motor comprising a supply circuit, a plurality of motors severally having armatures and field magnet windings, an auxiliary source of current, means for connecting the said source in circuit with the field magnet windings, means for connecting the motors to the supply circuit, with the respective armatures initially disposed in parallel-circuit relation and subsequently in series-circuit relation, and means for regulating the current in the field magnet windings of the motors to maintain the current generated in the motor armatures in excess of a predetermined value until the motor speed has diminished below a predetermined value. v

41. A system of control for braking electric motors comprising a supply circuit, a plurality of motors severally having armatures and field-magnet windings, an auxiliary'source of current, means for connecting the said source in circuit with the fieldmagnet windings, means for connecting the motors to the supply circuit, with the respective armatures initially in parallel-circuit relation and subsequently in series-circuit relation, a reversing switch for reversing the' connections of the field winding with respect to the corresponding armatures, and means for actuatin the said reverser when the motors are c anged to braking generators, irrespective of the former position of the said reverser.

42. The combination with a plurality of electric motors, a load driven thereby and means for effecting regenerative operation of the motors, with the respective armature windings initially connected in paral lel-circuit relation and subsequently in series-circuit relation for retarding the load until the motor speed has diminished below a predetermined value, of mechanical braking means for the load, and means for automatically applying 'the mechanical braking means when the regenerative braking operation of the motors ceases.

43. A control system for braking electric motors comprising a supply-circuit, a plurality of motors severally having armatures and field-magnet windings, a variable resistance, an anxiliary source of current, a single controller for connecting the said source and the said resistance in circuit with the series-connected field magnet windings and for regulating the resistance in accordance with the current generated by the motor armatures, and a single differential relay switch for automatically connecting the motors to the supply circuit, with the respective armatures initially in parallel-circuit relation when the voltage generated by the motor armatures attains a predetermined value, and means for subsequently connecting said armatures in operative series-circuit relation.

44. The method of continuous transition of a plurailty of regenerating motor windings from parallel to series-circuit relation that consists in disconnecting one winding, closing alocal braking circuit therearound including a portion of the circuit of a second winding, opening the circuit at said portion to dispose the armatures in series, and decreasing the resistance of said braking circuit.

45. The method of continuous transition 4 of a plurality of regenerating armatures from parallel to series-circuit relation that consists 1n disconnecting one armature, closing a resistance braking circuit therearound including a portion of the circuit of a second armature, opening the circuit at said portion to dispose the armatures in series, and excluding the resistance in the braking circuit. I

46. The method of regeneratively braking a plurality of electric motors drivinga common load and severally having armatures and field-magnet windings that consists in 'the following steps: first, connecting the motors to a supply circuit, with the respec-' tive armatures in parallel-circuit relation and the field-magnet windings inv seriescircuit relation to said parallel circuit; second, regulating the field strengths to maintain a substantially constant regenerated current untila predetermined motor speed is attained; third, effecting a continuous transition of the motor armatures from parallel' to series-circuit relation; and fourth, again regulating the field strengths to maintain a substantially constant regenerated current until a second predetermined speed 1 is attained.

47. The method of regeneratively braking a plurality of electric motors driving a common load and severally having armatures and field-magnet windings that consists in the following steps: first, automatiated current until a predetermined motor speed is attained; third, automatically effecting a continuous transition of the armatures from parallel to series circuit relation comprising disconnecting one armature, closing a resistance braking circuit therearound, including a portion of the circuit of a second armature, opening the circuit at said portion to dispose the armatures in series, and excluding the resistance in said braking circuit While inserting resistance in the field circuit; and fourth, again automatically regulating the field strengths to maintain a substantially constant regenerated current until a relatively low motor speed is attained.

48. The combination with a plurality of dynamo electric machines severally having armatures and field-magnet windings and severally adapted for both accelerating and regenerative operation, of means for simultaneously connecting said armatures in parallel-circuit relation and said field windings in series-circuit relation to said parallel circuit under regenerative conditions.

49. The combination with a plurality of electric motors severally having armatures and field-magnet windings, of switching means for simultaneously connecting said armatures in parallel-circuit relation, reversing the field windings with respect to the corresponding armatures, and connecting said field windings in series-circuit relation to said parallel circuit.

50. The combination with a plurality of 100 electric motors severally having armatures and field-magnet windings, of a switch adapted to occupy a plurality of positions two of which correspond to forward and reverse running of the motors, respectively, 105 and a third osition in which a plurality of contact mem ers are disposed to simultaneously connect the armatures in parallel-circuit relation, reverse the field windings with respect to the corresponding armatures, and 110 connect said field windings in series-circuit relation to said parallel circuit.

51. The combination with a plurality of electric motors severally having armatures and field-magnet windings, of a switch 115 adapted to occupy a plurality of positions two of which correspond to forward and reverse running of the motors, respectively, and a third postion in which a plurality of contact members are disposed to simultane- 120 ously connect the armatures in parallel-circuit relation, reverse the field windings with respect to the corresponding armatures, and connect said field windings 1n series-circuit relation to said parallel circuit, and 125 means for selectively positioning said switch.

52. The combination with a supply circuit and an electric motor, of means for regeneratively connecting the motor to,the supply circuit, an auxiliary braking apparatus, 1 

